1. Field of the Invention
This invention relates to an embroidery sewing machine which is used for forming embroidered patterns on a cloth. More particularly, it relates to an apparatus to cut a thread, which is used to form the embroidery patterns, in the embroidery sewing machine.
2. Description of the Prior Art
There is a conventional embroidery sewing machine having a construction as shown in FIG. 15A. A needle 304 moves up and down through a cloth placed on a throat plate 301 and a needle hole 302 of the throat plate 301. A looper 303 rotates synchronously with the needle. As a result, the cloth is stitched with a thread payed out through a thread insertion hole 303a of the looper 303. After the cloth has been stitched, a moving knife 306 advances in the direction of an arrow 310a and returns in the direction of an arrow 310b. While the moving knife is returning, a thread 311 between the needle hole 302 and the looper 303 is hooked on a hook portion 307 of the moving knife 306 as shown in FIG. 15B and is drawn towards a counter knife 305. The drawn thread 311 enters a guide portion 309 of the moving knife 306 as shown in FIG. 15C and is then cut by an edge 308 of the moving knife 306 and an edge 312 of the counter knife 305.
However, when the thread 311 between the needle hole 302 and the looper 303 is cut in the above mentioned embroidery sewing machine, there is a possibility that such portion of the thread 311 as extending from the thread insertion hole 303a of the looper 303 could be pulled into the thread insertion hole 303a of the looper 303 due to its own weight or the tension given beforehand to it. If the thread is pulled in this manner, it is impossible to hook the thread on the needle in the next stitching cycle with the same looper. Consequently there appears a problem that an operator is compelled to perform a troublesome work to manually pull the thread 311 out of the thread insertion hole 303a of the looper 303.
Furthermore, when the thread is cut in the above mentioned manner, the thread 311 near the guide portion 309 is heavily inclined to the return direction 310b of the edge 308 as is evident from FIG. 15C. It is difficult for the edge 308 to cut the thread 311 under such condition and there is a problem that a smooth thread such as a non-twisted nylon thread is apt to fail to be cut. Moreover, if the thread 311 is thick, it pushes apart the moving knife 306 from the counter knife 305 in the direction of an arrow 313 in FIG. 15D when the thread enters between the guide portion 309 and the counter knife 305. Thus the edges 308 and 312 can not be fitted to each other and there is a further problem that the thread 311 happens to fail to be cut.